The present application is a continuation of International Application No. PCT/SE2004/001458, filed Oct. 12, 2004, which claims priority to SE 0302740-6, filed Oct. 15, 2003, both of which are incorporated by reference.
The present invention relates to an arrangement for cooling a vehicle component disposed adjacent to an engine, which arrangement comprises a cooling circuit designed to feed a coolant through the vehicle component and comprising a line for coolant to the vehicle component and a line for coolant from the vehicle component.
The invention is particularly intended for cooling transmissions of the type employed in motor vehicles.
In connection with motor vehicles, there is a need for certain components, for example the engine and transmission of the vehicle, and other components mounted on or close to the engine, such as EGR valve (EGR=Exhaust Gas Recirculation), compressor, turbo, steering gear, etc., to be cooled. Not least, this requirement is great in heavy goods vehicles. Both an engine and a transmission contain oil, which is used in a known manner to lubricate and cool integral parts, for example in the form of the pistons of the engine and the gearwheels of the transmission. In addition, cooling circuits containing a coolant, for example water, are used to cool the engine and the transmission.
The need to cool the engine and the transmission stems from the fact that there is a risk of overheating of the engine oil and transmission oil respectively, especially under certain running conditions of the vehicle in question. This can result, in turn, in impaired lubricating properties for the oil, which, in turn, can lead to impaired functioning and reduced working life of the engine and the transmission.
In order to cool an internal combustion engine, it is known to use a coolant, expediently water, which, by means of a pump, is conducted in an external cooling circuit past a radiator and onward to the engine. In this way, the coolant will circulate in the engine and will subsequently be returned to the radiator by means of the pump. A corresponding cooling circuit can also be used to cool a transmission.
This solution, in which the coolant of the engine also cools the transmission oil, can work satisfactorily in certain situations. On modern engines, in which the cooling system often has a higher pressure and hence a higher temperature than corresponding older cooling systems, the solution does not work particularly well. The temperature of the cooling system is in this case higher than the recommended maximum permitted temperature of the transmission oil, the result of which is that the transmission oil is aged too quickly and the lubricating properties are poor. For instance, a cooling system can be 110° C. warm, but the recommended oil temperature of the transmission is 90° C.
An arrangement for cooling an engine is previously known through patent document US 2002/0112679, which arrangement comprises a first heat exchanger for cooling the engine oil by means of a coolant. The arrangement also comprises a second heat exchanger cooling the oil via heat exchange with an ambient air flow. The oil flow to the engine is normally directed via the first heat exchanger (and onward to the engine and its lubricating system), but a certain part of the oil flow to the engine can be directed by means of a restrictor to the second heat exchanger, in dependence on the engine temperature. The second heat exchanger is disposed parallel with the first heat exchanger.
US 2002/0112679 shows therefore that lubricating oil for an engine can be fed via a first radiator and a second radiator, but discloses nothing to solve the abovementioned problem concerning an increased cooling requirement of a transmission.
It is desirable to provide an improved arrangement for cooling, for example, a transmission, in which the above problem is solved.
In accordance with an aspect of the present invention, in an arrangement for cooling a vehicle component disposed adjacent to an engine, which arrangement comprises a cooling circuit designed to feed a coolant through the vehicle component and comprising a line for coolant to the vehicle component and a line for coolant from the vehicle component, the cooling circuit is also designed to cool the engine and comprises a further line for feeding the coolant to the engine, and the cooling circuit comprises a flow control valve for controlling the coolant in the cooling circuit such that the flow of coolant to the vehicle component is lower than the flow to the engine.
By virtue of an aspect of the invention, certain substantial benefits can be obtained. It may first of all be noted that aspects of the invention produce an effective cooling of a vehicle component, such as, for example, a transmission, with a cooling temperature that is lower than the corresponding temperature of the coolant that is fed to the engine. In addition, aspects of the invention create an arrangement for cooling a vehicle component that does not require, for example, a special coolant pump and special pipes for the transmission coolant. Instead, according to the invention, a common coolant pump is used to feed coolant both to the engine and to the transmission.
Preferably, according to an aspect of the invention, a cooling circuit is used, which, in turn, comprises two separate lines with two different temperatures. More precisely, these lines are in this case designed such that a lower flow is obtained in the line used to feed a coolant through the transmission compared with the line used to feed coolant through the engine. This results in an increased cooling capacity and hence a lower temperature for cooling the transmission than what was previously offered. This leads to benefits in terms of operation and service life of the transmission.